Containers for liquefied gases having corrigated wall structure

ABSTRACT

Integrated or membrane tanks for cryogenic fluids such as liquid methane are often provided with parallel sets of crossed corrugations in the thin metal lining of the tank to provide excess metal for accommodating thermal expansion and contraction, which corrugations must be around a corner where two walls meet. A folded formation is provided at the corner to prevent excess thermal strains. In this disclosure the formation at the corner is made larger in cross section than some of the corrugations into which it merges, and the corrugations increase in cross section as they approach and merge into the formations, thus enabling the corner formation to be of large size and reducing the stresses at the formation. A new and effective formation configuration is also disclosed.

United States Patent [72] Inventor Gilbert Jean Louis Massac Meudon, France [21 1 Appl. No. 809,742 [22] Filed Mar. 24, 1969 [4S] Patented July 27, 1971 (73] Assignee Conch Ocean Limited Nassau, Bahamas [32] Priority Mar. 26, 1968 (33] France [31 1 145,527

[ 54] CONTAINERS FOR LIQUEFIED GASES HAVING CORRIGATED WALL STRUCTURE .9 Claims, 5 Drawing Figs.

[52] US. Cl 220/72 [51] Int. Cl B65d 7/42 [50] Field olSeareh ..220/72,9,9

(56] References Cited UNITED STATES PATENTS l,96l,22l 6/1934 Hunter etal 220/72 X 3,215,301 11/1965 Armstrong 220/9 A 3,335,902 8/1967 Javorik..;.... 220/72 3,485,596 12/1969 Alleaume 220/63 X FOREIGN PATENTS 1,138,951 1/1969 Great Britain 220/63 1,171,684 2/1960 Germany 220/9 A Primary Examiner-Raphael M. Schwartz Attorney-Max L. Libman ABSTRACT: Integrated or membrane tanks for cryogenic fluids such as liquid methane are often provided with parallel sets of crossed corrugations in the thin metal lining of the tank to provide excess metal for accommodating thermal expansion and contraction, which corrugations must be around a comer where two walls meet. A folded formation is provided at the corner to prevent excess thermal strains. In this disclosure the formation at the corner is made larger in cross section than some of the corrugations into which it merges, and the corrugations increase in cross section as they approach and merge into the formations, thus enabling the corner formation to be of large size and reducing the stresses at the formation. A new and effective formation configuration is also disclosed.

PATENTEU JUL27 l9?! SHEET 2 [1F 3 A Home y CONTAINERS FOR LIQUEFIED GASES HAVING CORRIGATED WALL STRUCTURE This invention relates to containers for the storage and transport of cold liquids, such as liquefied gases at near atmospheric pressure, for example, liquefied natural gas. Such containers are used, for example, in marine tankers, for the transport of liquefied gases.

The invention is exclusively concerned with containers of the kind, known as integrated .tank containers, comprising a housing of load-bearing thermal insulation lined with a primary barrier against leakage of fluid,in the form of a thin and flexible fluidtight membrane tank of sheet material, e.g. metal, which is not subject tocold embrittlement, and'which is not self-supporting but is supported, against internal loads due to hydrostatic pressure and inertia forces, by the surrounding solid insulation. The insulation lines, and is itself supported by, a rigid'support'ingshell, so that the insulation directly transririts to the"'rigid supporting shell all the pressure exerted by the fluid upon the walls of the membrane tank.

Containers as defined in the preceding paragraph will hereinafter be denoted containers of the kind specified. f

The walls of the membrane tank of a container of the kind .specified will, unless prevented by external means, contract when contacted bythe cold liquid. The invention is exclusively concerned with containers of the kind specified and of the 'type in which the membrane tank is heldagainst overall dimensional change so that the membrane tank remains in contact with and supported by'the insulation and is formed with a double system of expansion and contraction corrugarality of corrugations extending parallel to one another in one direction and of identical cross-sectional sizeand another system 'of corrugations also parallel to each other and of constant cross-sectional size intersecting at right angles the corrugations of the first system and of a different cross-sectional size to that of the first system. These corrugations in two directions provide excess metal to accommodate contraction of the walls when contacted by the cold liquid so that the overall dimensions of the tank remain unchanged. In a container of this type, the corners of the membrane are formed by corner pieces having two corrugations and a central connecting formation, transverse to the corner and corresponding to the corrugations in the walls of the tank, the corrugations and the formation containing excess metal which permits expansion and contraction of the corner piece in the direction of .length of the corner.

" Containers asdefined in the preceding paragraph will hereinafter be denoted "containers of the type specified."

It is to be clearly understood that the term corner" is used throughout the specification to mean the junction formed by the edge portions of two adjoining walls, or portions of walls or of a sidewall and the top or bottom of the membrane tank. Thus theinvention is exclusively concerned with containers having plane walls or portions of walls which are plane. Such containers may be of any geometrical shape; they will usually be prismatic or parallelepiped but could be of more complex shape having walls comprising relatively inclined plane portions. Such a container may, for example, be shaped to fit in the forward part of a tanker. ln the case of a tank having plane sidewalls the angle of the dihedron may be substantially orthogonal or right, but it may be of any value, for example'an obtuse or acute angle depending upon the geometric shape of the tank. Some of the corners of a tank may be in the form of inner corners of solid angles which are internal or entrant. However, the tank may also have, particularly in the case of a tank having an upper extension or trunk, dihedral corners which are salient or reentrant.

Because the walls of the membrane tank are each formed with longitudinal and transverse corrugations of two different cross-sectional sizes, where the tank is rectangular or parallelepiped there will be three different forms of dihedral corner junction. In one form (a) the junction is between two corrugations of identical small cross-sectional size in the two walls. In another form (b) the junction is between two corrugations of large cross-sectional size in the two walls. In a further form c) the junction is between a corrugation of large cross-sectional size in one wall and a corrugation of small cross-sectional size in the adjacent wall.

Conventional corner pieces are each formed with corrugations and a connecting formation of the same size or sizes as the corrugations in the walls to be connected together. In one conventional arrangement the corner piece is formed by folding from flat sheet and the two limbs thereof are each formed with one corrugation of the appropriate size transverse to the corner and an aperture is formed in the plate at the corner between the two corrugations which is then closed by an initially separate'shaped gusset sheet'welded thereto and constituting a formation connecting the two corrugations. Thus, the corrugation in each limb is of a uniform size appropriate to the corrugation in the adjacent wall. The corner piece may have two large corrugations or two small corrugations or one small corrugation of constant cross-sectional size and one large corrugation of constant cross-sectional size. In any event the corrugations in the corner piece are connected by the formation constituted by the gusset sheet. This form of conventional corner piece has certain disadvantages. One disadvantage is the fabrication from two parts. Another disadvantage is that the comer piece, and particularly the gusset sheet is too stiff.There are slight fluctuations in use in the relative angle of inclination of two adjoining walls of a membrane tank, and hence of the two limbs of each corner piece connecting the two walls, and high stresses develop and the corner piece may shear or the gusset sheet may become separated from the corner piece.

In French Pat. application Ser. No. 944,844 (French Pat.

. No. l,447,9l3 corresponding to British Pat. No. 1,061,577)

there is disclosed a corner piece which is formed solely by folding from flat sheet to form two corrugations in the limbs of the comer piece which extend transversely of the corner and are connected by a complex folded formation adjacent the dihedral fold line. Moreover, French Patent of Addition 88,31 1 discloses various improvements or modifications of the construction of French Pat. No. 1,447,913. The constructions of these prior patents have certain advantages over the conventional construction. Because a corner piece of these constructions is folded from flat sheet without undue stressing it is less likely to become stressed in use notwithstanding slight variations in the relative angle of the two limbs of the corner piece. However, there are still stresses in the complex formation connecting the corrugations in the corner piece. This is particularly true in the case of a corner piece having two corrugations of small cross-sectional size since the formation has, heretofore, been of small cross section size which produces greater stresses. That is to say, it has been the practice in using this construction for the formation to be of a size corresponding to the size of the corrugations.

The aim of the present invention is to provide an improved construction of corner piece which is less likely to become highly stressed in use. A subsidiary aim is to provide a construction of corner piece which can be readily adapted for use at any of the junctions (a), (b) and (c) specified above.

According to the present invention there is provided, for a membrane tank of the type defined, an entrant dihedral corner piece with two corrugations transverse to the corner and meeting at the comer in a formation containing excess metal which permits contraction and expansion of the corner piece in the direction of length of the corner and at least one of the corrugations successively increases in cross-sectional size towards the formation.

The idea of the invention is that, by reason of the fabrication of the corner pieces with corrugations at least one of which successively increases in cross-sectional size towards the formation, the latter can be of sufficiently large cross-sectional size that the stresses are reduced to a minimum and the corner pieces are less liable to fracture. Thus the formation may be of a requisite constant large size irrespective of the size of the corrugations in the limbs of the corner piece, and the size of the corrugations in the walls connected thereby.

A comer piece in accordance with the invention for use at the junction (c) above will be formed in one limb with a corrugation of the requisite large cross-sectional size and the other limb will be formed with a corrugation which is of successively varying cross-sectional size, i.e. which is of small cross-sectional size at the edge of the limb for connection with the small corrugation in the relevant wall and increasing in cross-sectional size towards the dihedral angle for merging with the central formation.

In accordance with an important feature of the invention a corner piece for use in the junction (a) above, will have a formation of large cross-sectional size notwithstanding that the corrugations in the two limbs of the corner piece are of small cross-sectional size. Accordingly both of the corrugations in the limbs will each be of varying cross-sectional size tapering from a small cross-sectional size adjacent the edges of the limbs commensurate with the small crosssectional size of the corrugations in the walls to be connected and will progressively increase in cross-sectional size towards the center of the corner piece at the dihedral angle where they will be of a large cross-sectional size commensurate with the cross-sectional size of the central formation. The corner pieces in accordance with the invention will be used in conjunction with corner pieces, for use in the junction (b) above, in which the corrugations in the two limbs will be of a requisite large cross-sectional size commensurate with the large cross-sectional size of the corrugations to be connected.

Accordingly, comer pieces for use in the junctions (a), (b) and (c) above may all have central formations of constant cross-sectional size. That is to say, the corner pieces for use in the junctions (b) and (c) may have central formations of the same large cross-sectional size as the fonnation connecting corrugations of large cross-sectional size in a corner piece for use in junction (a). The description of the formation as being of a cross-sectional size corresponding to the cross-sectional size of the largest corrugations means that the formation gently merges with the corrugations but may be of complex cross section.

A feature of the invention resides in a membrane tank in which all of the entrant dihedral corner pieces have central connecting formations, connecting the corrugations therein, which are of identical cross-sectional size irrespective of the cross-sectional sizes of the corrugations in the walls connected by the corner pieces.

The corner pieces may be of any appropriate form. In particular the central connecting formation may be of any appropriate form provided that it connects and merges with the corrugations in the limbs and provides excess metal along the length of the dihedral corner for accommodating contraction. The corner piece is preferably but not essentially folded from a single flat sheet. In this respect the corner piece may be of the same general form as disclosed in French Pat. No. 1,447,913 or its Patent of Addition 88,311. Accordingly the central formation may be of complex cross section.

Preferably the corner pieces are formed from a single rectangular flat sheet which is folded to the requisite dihedral angle e.g. 90 and each of the two limbs is formed with a single corrugation extending from the free edge of the limb towards the central portion of the limb at the dihedral angle. At this central portion the corner piece is formed with a formation which merges with and connects the corrugations in the two limbs and provides excess metal for accommodating contraction along the length of the junction. This formation comprises a bridging convex corrugation of small cross section parallel to the corner and defined by U-shaped troughs merging with the respective corrugations in the two limbs.

Specific construction examples of the corner pieces will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a purely diagrammatic exterior isometric view of a cubic membrance tank, the walls of which are formed with parallel corrugations of small cross section and transverse parallel corrugations of large cross section, showing the different form of cornerjunction;

FIG. 2 is a general perspective view of a corner piece for use at junction (b);

FIG. 3 is a general perspective view of a corner piece for use at junction (a);

FIG. 4 is a general perspective view ofa corner piece for use at junction (c); and

FIG. 5 is a cross-sectional view taken on line V-V of FIG. 2.

In FIG. I the tank, generally designated 1, has a double system viz corrugations. That is to say each wall of the membrane tank is formed with a series of corrugations 2 extending convexly inside the tank and parallel to one another in one direction and of identical large cross-sectional size and another series of corrugations 3 extending convexly inside the tank and parallel to each other and of constant cross-sectional size intersecting at right angles the corrugations of the first system and of a smaller cross-sectional size than those of the first series. In the tank at the corner location designated (a) a junction between two corrugations in the two walls, viz. the sidewall 4 and top wall 6, of identical small cross-sectional size. At the location (b) there is a junction between two corrugations in the two walls i.e. the two adjoining sidewalls 4, 5 of large cross-sectional size. At the location (c) there is a junction between two walls, i.e. a sidewall 5 and a top wall 6 between a corrugation of large cross-sectional size in the top and a corrugation of small cross-sectional size in the sidewall.

The corner piece generally designated 7 shown in FIG. 2, is formed from a single rectangular flat sheet folded along the line 8 to the requisite dihedral angle, e.g. and each of the two limbs 7a, 7b is formed with a single corrugation 9, 10 extending from the free edge of the limb 7a, 7b towards the center of the corner piece at the dihedral angle 8. At this central portion the corner piece is formed with a formation generally designated 11 which merges with and connects the corrugations 9, 10 in the two limbs and provides excess metal for accommodating contraction along the length of the junction. This formation 11 comprises a bridging convex corrugation 12 having the general form of a trough of small cross section and defined by the U-shaped troughs I3 merging with the respective corrugations 9, 10 in the two limbs. The central portion of bridging corrugation 12 is preferably dimpled concavely as shown at 12' to provide a small creased trough parallel to the corner in the region that would otherwise be the high point of the bridging corrugation.

The corner piece 7 shown in FIG. 3, is identical with that shown in FIG. 2, except for the form of the corrugations 9, I0 in the two limbs of the corner piece. In particular the formation II is of the same large cross-sectional size. However, each of the corrugations 9', 10', in the two limbs, which are identical with each other, is of progressively changing cross-sectional size. Thus, each corrugation 9, 10 comprises a portion 9a, 10a adjacent the edge of the limb of small constant section and one adjacent portion of 9b, 10b of progressively increasing cross-sectional size extending towards and merging with the central formation 11.

The corner piece shown in FIG. 4 is identical with that shown in FIGS. 2 and 3, except that the corrugation 9 in one limb is of the same large cross-sectional size as the corrugation 9 in one of the limbs of the corner piece in FIG. 2, whereas the corrugation 10" in the other limb of the corner piece is identical with that of IO in the limbs of the corner piece of FIG. 3.

I claim:

I. A sheet metal corner piece for prismatic cryogenic tanks having sheet metal walls with stress-relieving linearly extending wall corrugations extending perpendicular to dihedral corners of the tank,

said corner piece having at least two corner corrugations transverse to the corner and matching respective wall corrugations in two of said sheet metal walls,

said comm nism at the corner in a formation containing'exce'ss metal which permits contraction and expansio'n of the Icorn'erf piece in thedirection of length'of.

at least one of said corner corrugations increasing in crosssectional size'toward the formation.

' I 2. For use in a corner junction between two linearly extend- "ing wall corrugations of identical small cross-sectional size in two sheet metal walls which meetat a corner,

a corner piece having short corrugations each of varying cross-sectionalsizeltapering from a small cross-sectional size adjacent'the edges of the corner piece commensurate with the smallcross-sectional size of the corrugations in the walls to bev connected and progressively increasing in --cross-sectional size toward the center of the corner piece atthe'dihedral tional size,

i a central folded formation at the comer line of said comer piece, said formationproviding excess metal for accom- 'modatingcontractioii and expansion along the length of the comer junction, said central formation merging smoothly into said short tapering corrugations at their larger end.

i3. For use in a container ofthe type specified, a dihedral, sheet material'corner piece having two corrugations, one in each limb of the corner piece and meeting'at thevangle of the comer in, a formation containing an excess area of, material 'pennitting contraction'and expansion of the comer piece in the direction of length of the corner,

at least one of the two corrugations successively increasing anglewhere they are of a large cross-sec- 4; A cornerpiece according to claim 3, folded from a single flat sheet 5. Acorner piece according to claim 4, wherein the formation comprises a convex bridging. section between two U- shaped troughs transverseto the respective corrugations in the two limbs.

6. A corner piece according to claim 5 wherein the bridging section is formed with a concave of corrugation of small cross section parallel to the corner.

7.A comer piece according to claim 3, wherein one of the corrugations is of uniform size, equal'to the maximum size of the other. 5

8. A comer piece according to claim 3 wherein both corrugations increase in size towards the formation.

' 9. For use in a'sheet metal container subject to large temperature variations and having at least two sheet metal walls meeting at a corner, said walls having spaced inwardly convex corrugations with plane wall sections between them,

a sheet metal corner piece having corrugations matching the corrugations of said two walls, I

said last corrugations meeting at the comer line of the corner piece in a central folded fonnation, said formation providing excess metal for accommodating contraction and expansion along the length of the corner line,

said folded formation comprising a bridging inwardly convex corrugation merging through two respective inwardly concave corrugations with the respective wall-matching corrugations of said corner piece,

the centralportion of said bridging corrugation being dimpled inwardly concavely to provide a small creased trough parallel to the corner line in the region that would otherwise be the highest point in the convex bridging cor- 'rugation. 

1. A sheet metal corner piece for prismatic cryogenic tanks having sheet metal walls with stress-relieving linearly extending wall corrugations extending perpendicular to dihedral corners of the tank, said corner piece having at least two corner corrugations transverse to the corner and matching respective wall corrugations in two of said sheet metal walls, said corrugations meeting at the corner in a formation containing excess metal which permits contraction and expansion of the corner piece in the direction of length of the corner, at least one of said corner corrugations increasing in crosssectional size toward the formation.
 2. For use in a corner junction between two linearly extending wall corrugations of identical small cross-sectional size in two sheet metal walls which meet at a corner, a corner piece having short corrugations each of varying cross-sectional size tapering from a small cross-sectional size adjacent the edges of the corner piece commensurate with the small cross-sectional size of the corrugations in the walls to be connected and progressively increasing in cross-sectional size toward the center of the corner piece at the dihedral angle where they are of a large cross-sectional size, a central folded formation at the corner line of said corner piece, said formation providing excess metal for accommodating contraction and expansion along the length of the corner junction, said central formation merging smoothly into said short tapering corrugations at their larger end.
 3. For use in a container of the type specified, a dihedral sheet material corner piece having two corrugations, one in each limb of the corner piece and meeting at the angle of the corner in a formation containing an excess area of material permitting contraction and expansion of the corner piece In the direction of length of the corner, at least one of the two corrugations successively increasing in cross-sectional size towards said formation, the other corrugation being of a minimum cross-sectional size greater than the minimum cross-sectional size of the first.
 4. A corner piece according to claim 3, folded from a single flat sheet.
 5. A corner piece according to claim 4, wherein the formation comprises a convex bridging section between two U-shaped troughs transverse to the respective corrugations in the two limbs.
 6. A corner piece according to claim 5 wherein the bridging section is formed with a concave of corrugation of small cross section parallel to the corner.
 7. A corner piece according to claim 3, wherein one of the corrugations is of uniform size, equal to the maximum size of the other.
 8. A corner piece according to claim 3 wherein both corrugations increase in size towards the formation.
 9. For use in a sheet metal container subject to large temperature variations and having at least two sheet metal walls meeting at a corner, said walls having spaced inwardly convex corrugations with plane wall sections between them, a sheet metal corner piece having corrugations matching the corrugations of said two walls, said last corrugations meeting at the corner line of the corner piece in a central folded formation, said formation providing excess metal for accommodating contraction and expansion along the length of the corner line, said folded formation comprising a bridging inwardly convex corrugation merging through two respective inwardly concave corrugations with the respective wall-matching corrugations of said corner piece, the central portion of said bridging corrugation being dimpled inwardly concavely to provide a small creased trough parallel to the corner line in the region that would otherwise be the highest point in the convex bridging corrugation. 